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Still a comparatively small part of the automotive landscape, electric cars and plug-in gas-electric cars often elicit questions such as, “What about the battery?” or “How long will the battery last?”

The implication may be first adapters are sort of like the crew of Star Trek: “Boldly going where no man has gone before.”

Critics and advocates have alternately come up with answers to battery longevity questions citing data that makes them respectively frown or smile, but the short answer is this: Ultimately, it is too soon to tell.

Then again, when the first gasoline cars started to come along, and people compared those noisy, smelly, breakdown-prone and flammable contraptions to horses, while fence sitters stuck with what was known reliable, well, you know the rest of that story.

But similarities and differences between internal combustion engines and motors powered by software-controlled batteries make that oft-used analogy an imperfect one.

There may be good reason why people are waiting to see what generation two and three bring beyond today’s top-selling Nissan Leaf, Tesla Model S, extended-range Chevy Volt and other “compliance cars” their makers only lease and may not even let you buy.

Hesitancy may also be due to lack of knowledge and/or fear of the unknown.

Sometimes clinging to a comfort zone is the right thing to do, and at others, it may only feel right even if it’s not.

Warranted

To increase consumer confidence, manufacturers have warranted the batteries for time periods deemed pretty long even by internal combustion car standards.

Typically it’s eight years, and mileage is usually at least 100,000 miles. Tesla warranties its 60-kwh Model S to 125,000 miles, and the 85-kwh version gets unlimited miles.

Nissan warrants the Leaf’s battery against defects for 8 years/100,000 miles. It projects its life for at least 10 years, with the expectation that you’d have around 60-70 percent battery life at that point, depending on usage patterns.

Studies

Research has been conducted but in most cases, electric cars looked at were only a year or two old, with well under 100,000 miles, if not less than 50,000 miles. They were all under warranty, but some useful preliminary data can be derived from these.

What may be one of the more useful studies is Plug In America’s look at the Tesla Roadster. This study was done in 2013 just when the five-year warranty of the first Roadsters was ending, and showed Tesla had exceeded early expectations given for its cars.

Launched in 2008, the Roadster was the first EV of the modern era and cost in the low six figures. Tesla built fewer than 2,500, and the study observed, “as of July 4, 2013, Tesla Motors reports that ‘2,100+ Roadsters’ have been driven over 35 million miles.

Biases in the study may have been for or against as (only) 126 respondents who’d driven over 3.1 million miles collectively were at least motivated enough to fill in a survey.

However somewhat overlapping findings from anonymous data collection software on 106 Roadsters added up to a suggestion that “on average, a Roadster battery pack will have between 80% and 85% of original capacity after 100,000 miles.”

That means if its EPA-rated range was 248 miles, it may have 198-211 miles range, more or less after 100,000 mile usage.

As a reminder, a plug-in car’s battery pack is essentially like the fuel tank on a regular car. It is the most expensive component, and no one who buys a gas or diesel-powered car expects the miles of range to diminish, which may be unsettling for some.

“The balance to this issue is all of the positive aspects of driving electric: smooth instant acceleration, convenient fueling, one-fifth the fuel cost, much lower maintenance costs,” he said.

Indicators so far are the Model S is doing better than the Roadster but Saxton is not making forecasts yet though he notes owners participating in an ongoing survey are averaging over 18,000 miles annually.

“We may see Model S owners passing the Roadster record in the next year or two. There are three on the survey that are over 40,000 miles already (14 to 19 months old),” he said.

An interesting read is Tesla’s owners manual including warnings on page 83 not to let the battery go to zero, or else.

The Leaf did suffer excessive range loss among a small number of drivers in hot climates, which Nissan acknowledged by upping its warranty but not re-engineering its pack.

This is one point on which Ford’s 50-state-available Focus Electric may have a competitive advantage, as observed by Ford spokesman Aaron Miller in response to our question: “What is the fastest way to “kill” (or degrade) the battery?”

“Extreme battery temperatures and aggressive drive patterns will impact its life and performance,” he said, “and hence it’s important to have an effective cooling and heating system to regulate temperature for these demanding applications.”

That said, some Leafs in Saxton’s study observed no noticeable degradation in the hottest climates, so there are no absolutes.

What’s more, INL tested in Phoenix, Ariz., the epicenter of where climate also has been reported as attacking the Leafs which use only air cooling, and no liquid thermal management system as does Tesla, Chevrolet, Ford, Honda, and others.

Tesla, as is well publicized, is even more adamant about its higher-powered Superchargers as safe, and no problem. There are still however conservative voices out there saying too-frequent high-kilowatt dumps into li-ion packs can diminish their lives.

Tesla and Nissan at first did warn against it, but have since said it’s OK, and contrarily, battery engineers at Ford suggest caution is still warranted.

“In general, DC fast charging will increase the stress level that the battery will experience,” said Miller. “Frequent use will further increase this stress level. The exact impact on battery life would very much depend on the battery cell design, chemistry and application.”

Whether concerns remain, the convenience of recharging 80 percent in 20-30 minutes has weighed into decisions to go with DC quick charging. In the case of an 84-mile rated Leaf, it can effectively double or triple this range making daily long-distance driving more feasible for first adopters.

Long-Term Prognosis?

A measure of research and personal assurance is required for those who buy and don’t lease their electric cars as no one has seen an eight-year-old Tesla Model S, or Chevy Volt or Nissan Leaf, for example.

One simple way around it, where possible, is leasing which puts all liability on the long-term ownership back on the manufacturer.

GM Volt engineers included several from Hughes, the world’s largest satellite and deep-space supplier, who devoted their careers to proof-testing, failure mode analysis/prevention, and accelerated life testing of batteries that could last 17-20 years. While the Volt does not have an aerospace battery, it’s believed to be well engineered, and built to last to automotive standards.

While they do vary, some lease prices around the country have been so low that the cost of the car-plus-electricity can be less than cost just to fuel some ordinary cars.

This is like getting a car “for free” as proponents point out, and there is something to that, where applicable.

For those who wish to own beyond the warranty period, desires for aftermarket battery suppliers to spring up in due time have been uttered, but it may be a while before the business case for such an industry is justified.

There’s also hope that as battery costs come down, the stock replacement or repair may be cheap enough to make nursing the car longer worthwhile. Already GM’s parts dealer list price is only $3,000 for the Volt replacement with core exchange, but a supplier listing one for under $2,600 admitted it cannot actually sell one, and the order must go through an authorized technician.

Produced since 2011, the Ford Focus Electric has a battery warranty of 8 years / 100,000 miles and 10 years / 150000 mile in green states – California, Connecticut, Maine, Maryland, Massachusetts, New Jersey, New York, Oregon, Pennsylvania, Rhode Island, Vermont, and Washington.

Certainly, however, advocates are already keeping their cars alive one way or another. One Avi Hershkovitz is listed as the owner of a 2002 RAV4 EV with 243,000 miles and only one pack replacement so far.

As for batteries in EVs that are totaled or worn out, myriad secondary usages are being developed, or alternately, recycling is expected to keep them out of land fills, as their metals and rare earths are valuable.

We’ve linked studies and data for you to do further study, but where EVs are leagues ahead of the horseless carriages of over 110 years ago is they are building on the shoulders of modern automotive engineering.

Only the powertrain is unique, and otherwise all-electric cars are conventional and familiar automobiles. Further, electric powertrains are simpler with far fewer moving parts, and in theory, have less to go wrong.

Sales have been slowly increasing, and talk of the next generation gas-electric Volt and all-electric Leaf is now underway for maybe 2015/2016.

But, as Saxton points out saying he did not wait for the first computers to level out before he decided to buy his first, the same goes for electric cars.

“Personally, I think there’s much less to worry about with EV battery longevity than there is with the volatile global oil market. We’re always one big storm, one terrorist attack, one surprise announcement from an oil dictator away from $8/gallon gas and rationing. I know the cost of electricity won’t suddenly double overnight,” said Saxton. “For most people, by the time their battery pack has lost significant capacity, they will have saved more than enough in gasoline costs to cover any associated loss in value.”